Conventionally, when a plate-shaped substrate or other member is to be exposed, accurately managing the exposure position thereof has been achieved by, e.g., using a substrate having a predetermined marking applied to its surface, and using the marking to determine the position of an exposure mask (e.g., Patent Documents 1 to 3), or installing a registration pin on a pallet on which the substrate is placed (e.g., Patent Document 4).
However, in a case where a film is to be exposed and the film is continuously supplied into an exposure apparatus, as in a roll-to-roll format, then it is difficult to apply the above registration technique used when exposing a plate-shaped member. That is, on a roll-to-roll film production line, the film to be exposed is supplied into an exposure apparatus 1 in, for example, a step as is illustrated in FIG. 9, and unlike when a plate-shaped substrate or the like is being exposed, the film 2 being conveyed is more likely to undulate due to its flexibility.
Furthermore, on the roll-to-roll film production line illustrated in FIG. 9, a treatment that makes use of the flexibility of the film is carried out at all processing steps. That is, a film 2 is unwound from a supply reel 80, supplied to the line, and dry cleaned, surface-modified, or otherwise pretreated in a pre-treatment unit 3. A predetermined exposure material is applied to the surface with a slit coater 4, and the applied exposure material is dried in a drying apparatus 5. The film 2, with an exposure material coating formed on its surface, is supplied to the exposure apparatus 1, and the exposure material coating is exposed using the exposure apparatus 1. During this time, the film 2 is supported by, for example, rollers 9 between each of the apparatuses, and is conveyed by the rotation thereof. Accordingly, it is difficult to apply the techniques disclosed in Patent Documents 1 to 4 for the exposure of the film 2 in a roll-to-roll format.
In a case where a film is being exposed in a roll-to-roll format, it is very important to maintain a relative positional relationship between the film and the mask, in order to heighten the exposure accuracy. For example, Patent Document 5 discloses a technique for positioning a mask with respect to a film. Namely, the technique disclosed in Patent Document 5, in which case one sheet of film undergoes two separate cycles of exposure, is adapted for subjecting the film to a first cycle of exposure to form a pattern and thereafter, in the second cycle of exposure, adjusting the position of the mask by using a line charge-coupled device (CCD) to detect the pattern formed by the first cycle of exposure. As in FIG. 2 of Patent Document 5, two side edges of the film in the width direction are not part of the exposure region.
FIG. 10 illustrates by way of example a conventional exposure apparatus of a model where exposure light sources 11 for emitting an exposure light are arranged face-to-face so that one pair corresponds to one mask 12, and irradiate the exposure light from mutually different directions. An exposure apparatus of such a model has been used to expose an oriented material coating in the formation of, for example, a colorless, translucent oriented coating on a glass substrate such as a liquid crystal display or on a film base material such as a polarizing film. Namely, one practice in a case where an oriented coating is formed by exposure using the exposure apparatus is to supply into the exposure apparatus a member to be exposed having a colorless, translucent oriented material coating formed on the surface, and irradiating same with an exposure light from different directions in equal intervals of a predetermined region to form an oriented coating that has been oriented in different directions. According to the exposure apparatus of such description, it would be possible to, for example, segment a region of the film corresponding to one picture element into two in the width direction thereof, or to respectively segment the film in the width direction thereof into regions corresponding to one pixel, and form an oriented coating with different orientation directions respectively in each of the segmented regions. This feature of the orientation direction of the oriented coating causes the liquid crystal molecules sandwiched between glass substrates to behave differently when a voltage is applied, depending on the orientation direction of the oriented coating, and this makes it possible to broaden the angle of view of a display apparatus while also enabling the resulting film to be used as a polarizing film for a three-dimensional (3D) display or the like. Of late, there has been growing focus on such techniques of film exposure.
When a film is exposed using such an exposure apparatus, the film is susceptible to undulating while being conveyed, causing deviation in the exposure position. In order to reduce the impact of this deviation in exposure position, one practice of exposure with, for example, an exposure apparatus where a plurality of light sources is arranged side by side in the direction of movement of the film as described above has been to use a plurality of masks 12 and not just one mask, as illustrated in, for example, FIGS. 10 and 11, where each of the masks 12 is arranged in a staggered fashion so as to be side by side in the direction of movement of the member to be exposed and the width direction perpendicular thereto, and a exposure light source 11 is provided for each of the masks. The exposure light from the exposure light sources 11 is then transmitted through masks 121 to 124 and, as illustrated in FIG. 11, on an upstream side from which the film is being supplied, the film 2 is exposed at exposure regions A and C by the masks 121 and 122, which are arranged spaced apart from each other, while on the downstream side a region B between the exposure regions A and C is exposed by the mask 123 and a region D adjacent to the exposure region C is exposed by the mask 124. This makes it possible to accurately form a pattern of segmented orientation on substantially the full surface of the film 2.